91影视

Figure 33-42 is the system of three polarizing sheets.

Figure 33-43 is the graph of l vs$胃$ .

Use the concept of change in the intensity of light due to polarization. First, find the angles for the three sheets. Using the equation of intensity for angle, find the fraction of intensity.

Formulae are as follows,

$I=I_0{\cos }^2胃$

Where, l is the intensity.

From the graph, the curve is zero at${胃}_2=0^0\text{and}{90}^0$. That means sheet 2 is perpendicular to one of the other sheets at${胃}_2=0^0\text{and}{90}^0$.

For$胃=0^0$, the first and second sheets are parallel andthethird sheet is perpendicular.

At $胃={90}^0,$the second and third sheets are parallel and first sheet is perpendicular.

$$\begin{gathered} {胃}_1=0^0 \\ {胃}_3={90}^0 \end{gathered}$$

Given${胃}_2={30}^0$

The intensity of light fromthefirst sheet as,

$I_1=\frac{1}{2}{I}_0$

The intensity of light fromthesecond sheet as,

$$\begin{gathered} I_2=I_1{\cos }^2({胃}_2鈭�{胃}_1) \\ {I}_2=I_0{\cos }^2{30}^0 \\ {I}_2=\frac{3}{8}{I}_0 \end{gathered}$$

Similarly, intensity of light from the third sheet is,

$$\begin{gathered} I_3=I_2{\cos }^2({胃}_3鈭�{胃}_2) \\ {I}_3=\left(\frac{3}{8}\right)I_0{\cos }^2({90}^0鈭�{30}^0) \\ \left(\frac{3}{8}\right)I_0{\cos }^2\left({60}^0\right) \end{gathered}$$

$I_3=\frac{3}{22}{I}_0$

So the fraction of light as,

$$\begin{gathered} \frac{I_3}{I_0}=\frac{3}{32} \\ \frac{I_3}{I_0}=9.4\% \end{gathered}$$

Therefore, the percentage of the light鈥檚 initial intensity transmitted by the system when ${胃}_2={30}^0$is$\frac{I_3}{I_0}=9.4\%.$